The Gene Expression and Control Unit of the Clinical Gene Therapy Branch (CGTB) is focused on two areas of research (i) Molecular Mechanisms of Transcriptional Regulation and Targeting and (ii) Gene Therapy of Cancer and Metabolic Disorders The study of transcription regulatory molecules is of seminal importance because it provides information of the fundamental mechanisms that regulate spatial and developmental gene expression in vivo. Our approach is to study the interplay between regulatory sequences and the corresponding transcriptional factors. We are particularly interested in the role of two members of the CCAAT Enhancer Binding Protein (C/EBP) family, C/EBP-alpha and C/EBP-epsilon, in cell proliferation and differentiation of hepatocytes, adipocytes and hematopoietic cells respectively. We study their the functional roles in vivo using homologous recombination for targeted interruption of both genes and for conditional inactivation of C/EBP-alpha. Furthermore, study semi-synthetic cell-specific transcriptional elements for potential use in targeted transcriptional gene therapy strategies. The other major focus of our laboratory is the development of novel vectors for cancer gene immunotherapy and controllable methods of gene expression of transgenes in vivo. Cancer immunotherapy holds great promise because it may facilitate the use of therapeutic vaccines for the treatment of tumors. We seek to generate a combined approach which may have high potential therapeutic value for several human cancers. This strategy is based on (i) highly efficient alphaviruses, e.g. Semliki Forest Virus (SFV) and (ii) hybrid Adenoviral/SFV chimeric vectors. SFV has several advantages over existing vectors: efficient autocatalytic cytoplasmic replication, late onset of cytopathogenic effects, broad host range and genome of positive polarity. We envisaged that the combination of localized high levels of expression of HSV-TK with a "programmed" oncolycate due to the cytotoxicity of SFV particles will have a synergistic effect in promoting rigorous tumor rejection and enhancement of long-term survival of our animals in an experimental malignant glioma model.